My doubt is why we choosing fragment over activity even i too read that it is reusable i has its own life cycle etc etc. But as a beginner its quite difficult to work on it . Then i Have an another doubt to so far what i did in my project is i have only two activity one is for login and another one is for navigation drawer and action bar rest of things are all fragment which comes under activity 2 is it right way to do with or am making mistake . Many fragments are coming under activity 2 like multiple fragment inside a fragment is it right way it may be dumb question as a beginner is quiet difficult to understand for me can anyone clarify my doubt
Fragments were invented for tablets in order to combine several fragments on one screen. Most commonly they are used in master detail relationships. Look at this question from this point of view. Does it make sense to put two fragments on one screen? Are they connected?
Read this article one more time to clarify when fragments are needed. http://developer.android.com/guide/components/fragments.html
1) You don't have to use fragments if you don't feel they are necessary for your application.
2) Having multiple activities is fine. Most applications do.
3) Having fragments inside fragments is permissible, but you should just be aware that it can cause odd behavior in your application if you are not familiar with the lifecycle events.
4) In the Android Dev Summit (2015), a great overview of a sample Android architecture was presented, I encourage you to view it: here
Hope this helps to clarify things some.
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I am new to android and I want to develop a multi page sign up form. I want to know that I should use one activity for each page or it is a better approach to use fragments as I need to keep all data from each page to submit in database finally.
Thanks
This was a topic covered at Google I/O this year in a talk called What the Fragment.
The basic rule is that if a feature is meant to be reused along with split mode in landscape or tablet, then definitely use a fragment.
If the code is a reusable bit of functionality that may show up as a dialog or functionality in an other Activity then use a fragment.
Something that is discouraged is the use of multiple fragments to piece together an activity. I've seen a fragment with nothing but a button embedded in multiple activities. That's not good.
There is some discussion around how useful fragments are. Lyft came up with an alternate that uses views, called Scoop. If you want to swap a lot of Views, look in to that definitely.
For your need, the answer depends on how complex each for is. If there are a lot of fields on each form, with complex validation logic I would put it in an activity. Juggling fragments can be tricky if the users can skip bank and forth in the form. If the forms and interaction with them if simple, use fragments or even hidden views.
I've developed an android phone app in which the navigation is mostly activities and starting activities for results. I've read that in order to make the tablet layout look like 2 screens of my phone app one next to the other I should have made it with fragments. Is there another way to migrate my functionality to the tablet app? Meaning to keep the start activity for result but just concatenate two activities on screen? (it may sound stupid, I know). Thanks
In order to keep the software design simple and modular, fragments come in really handy. You can use the same fragment's UI design + working code in multiple places without changing much functionality.
Since you have the code built and running in terms of activities, it won't take much time to migrate/port it to a Fragment since the life cycle methods are pretty similar. All you need to do is study the life cycle of a Fragment and move code chunks from the Activity to the Fragment class.
You can study all about Fragments here - http://developer.android.com/guide/components/fragments.html
or maybe a training session here will help you more -
http://developer.android.com/training/basics/fragments/index.html
You will learn a lot and once you have tried it you will be able to comprehend the advantages in a much better way. In future always make it a point to design in terms of Fragments to have a much modular design.
Along with that I think you will also need to learn to design layout for multiple screen sizes. This link over here will help you understand how to support multiple screen sizes -
http://developer.android.com/guide/practices/screens_support.html
If a tutorial to do this very quickly is what you seek then this should help -
http://www.101apps.co.za/index.php/articles/converting-android-activities-to-fragments.html
All the best :)
It very depends on your app GUI structure. Sometimes, you even not need to adapt your GUI for tablet (if you build interface dynamically basing on screen dimension). As rule, if you have two screens where one screen is advanced or logical extension of other then you can union it into one screen on tablets for better informativeness. Secondary way, as rule, based on fragments.
You can achieve it with help of Activity group but it is deprecated in Api level 13, for more details please visit http://developer.android.com/reference/android/app/ActivityGroup.html, but I will suggest to go with Fragment as Fragment having nearly similar life cycle like as Activity with extra methods and features. Please refer link for more details http://developer.android.com/guide/components/fragments.html
All the reasons I can find for using Fragments in Android activities have to do with having the ability to display multiple classes/view in the same screen, encapsulating multiple logical components, etc.
Considering all this, it seems, fragments are only actually useful when you employ the use of many of them.
Is that so? Is there ever a point of using just one fragment in an activity?
I ask now because I saw an option on Android Studio to do just that, and I am wondering what the point is.
Out of my personal opinion, I would say yes.
For the following reasons:
Assuming you are familiar with Fragments, creating a Fragment is hardly any extra work plus has the following benefits
Fragments can easily be reused somewhere else (possibly another Activity that has more Fragments, furthermore, Fragments do not necessarily need to use up the full screen).
Activity transitions are more expensive, Fragment transitions are more sophisticated.
The Fragment animation framework is better (in terms of usability and performance).
I always like to keep the number of Activities to a minimum which keeps the AndroidManifest.xml short and clean.
UI separated into Fragments leads to cleaner code structure and easier code maintenance.
According to google coding guidelines, it is best practice to create as few Activities as possible, and create multiple Fragments instead that are switched inside an Activity.
Well it depends, if you are going to use that fragment in another activity yea, you have a "point" and maybe in a future you can reuse it on another activity, but in the case for example of a splash screen well, it don't have a point. All depend in the uses you want to give to your application.
Pros:
-> reusable piece of code
easy to utilize it again in any module
easy to debug
-> handles orientation changes better than activity using setRetainInstance(true)
-> great help when scale the app in future for multipane layouts or multi-screen support
Cons:
-> little overhead and time consuming if you are not familiar with fragments
I have read the documentation and some other questions' threads about this topic and I don't really feel convinced; I don't see clearly the limits of use of this technique.
Fragments are now seen as a Best Practice; every Activity should be basically a support for one or more Fragments and not call a layout directly.
Fragments are created in order to:
allow the Activity to use many fragments, to change between them, to reuse these units... ==> the Fragment is totally dependent to the Context of an activity , so if I need something generic that I can reuse and handle in many Activities, I can create my own custom layouts or Views ... I will not care about this additional Complexity Developing Layer that fragments would add.
a better handling to different resolution ==> OK for tablets/phones in case of long process that we can show two (or more) fragments in the same Activity in Tablets, and one by one in phones. But why would I use fragments always ?
handling callbacks to navigate between Fragments (i.e: if the user is Logged-in I show a fragment else I show another fragment). ===> Just try to see how many bugs facebook SDK Log-in have because of this, to understand that it is really (?) ...
considering that an Android Application is based on Activities... Adding another life cycles in the Activity would be better to design an Application... I mean the modules, the scenarios, the data management and the connectivity would be better designed, in that way. ===> This is an answer of someone who's used to see the Android SDK and Android Framework with a Fragments vision. I don't think it's wrong, but I am not sure it will give good results... And it is really abstract...
====> Why would I complicate my life, coding more, in using them always? else, why is it a best practice if it's just a tool for some cases? what are these cases?
I am sorry if I wrote too much, and thanks for your time. I hope I will get your attention, because I really need ideas and experiences about this topic.
Best regards, Ahmed
You shouldn't always use fragments. Fragments have their uses, such as when you want to page in and out parts of the screen or when you want to drastically change the UI in different orientations. When they make sense, use them. When they don't, skip them. I find they make sense in maybe about 10-20% of apps- I rarely see the need.
If there's a certain positive aspect apart from the simpler reuse of logic through different layouts, it's the ability of Fragments to be kept alive by the system at orientation change, aka while an Activity is reconstructed from zero, a Fragment can retain its instance, and therefore using them is more stable than an Activity. Also, switching between Fragments is quicker.
Personally, if I don't need to mess around with different orientations and layout sizes, I still prefer using Fragments and a singular container Activity around it, for stability and seamless switching between the different screens.
Its quite a general question and not directly related to a specific programming problem. But in my opinion good software is based on good design and therefore a good understanding and best practices. So your question is a good one for stackoverflow.
So, what about fragments. It took me a while to understand why you could or even should use them. As #pskink said, you can easily live without them. But if you are planning to rollout your software on different devices, you should definately think about fragments.
The screen resolution and density is not the only problem. Think about a smartphone. The screen is much smaller, so you can not present your app the same way as you can on a tablet. For instance a master detail flow. Left side, a list of elements and when you click one element, you will see details of that element on the right side. Easy to do on a tablet. But on a smartphone you would put the master-view into one fragment and the detail-view into another one.
You got two options to realize that scenario. Either programm different activities for smartphone and tablet but because they are actually doing the same logic, it's better practice to put the logic into fragments and reuse those fragments in two layouts (phone/tablet).
In an Android app, I have two screens* the user sees, one for preparing a query and the other for displaying the results. The right UI here is to have the query preparation in one screen, and then see the result on the second screen. Since this app is aimed at phone users, there's no need to display the two at once.
The traditional Android way is to use two activities, a QueryPreparationActivity and a DisplayResultActivity, and switch between the two. However, I've been hearing more and more about how the Android UI is switching to fragments. I can implement the two screens as two fragments and have the activity switch them, but is it worth the trouble? I will essentially be reproducing the Activity management code Android already has.
Is there a reason to use two fragments here?
*I'm using the term screen, because it isn't necessarily an activity...
Personally, I always develop using Fragments.
But the best reason I can give you for using Fragments is when you develop for handset and tablet devices you get a lot of reusability.
I know you already mentioned that there is no need to show both screens at once. But say later you were to develop the same "screen" for a tablet device and realize that the preparation screen is too barren and want to have both queryprep and display result show at the same time, you would have to write a totally new 3rd activity.
If you used fragments, you would reuse your 1 activity and 2 fragments, and that activity should be coded smart enough to determine the size of the screen and show the proper layout.
Code Reusability & Flexibility are the buzz words here.
If you have any questions please leave a comment and I will expand my answer. If you like my answer, please upvote and accept.
Fragments were introduced encapsulate UI elements and related behaviour into a single, reusable module. Before fragments you had to re-write the much of the same code that 2 or more activities had in common especially if you couldn't find a good approach to abstract the UI/control code into a super class. This was further complicated by the limitations that activities only call setContentView once. So sharing some code between activities wasn't all that nice.
Now, to answer your question, it all depends on you. If you think that further down the road you could use the QueryPreparation or DisplayResult ui as a module (layout and logic behind it) then go for the fragment implementation. It could be a different layout for landscape view on phone or if you decide to support smaller tablets like the nexus 7. If you are sure that it will never happen then stick with activities. Personally, I use fragments everywhere and they are a sure way to "future proof" your implementation for reuse down the road.
In short Fragments were introduced to accommodate the emergence of tablet/large screen devices and allow developers to create applications that will run across a wide range of screen sizes with very little change to code.
More can be read here at the Android Blog. That blog also details some of the finer technical details for the reasons for the move toward Fragments. Also introduced at Goolge IO 2012 were DialogFragments which you should consider using instead of Dialogs. Another blog post here describes them.
You're better off getting used to using Fragments and DialogFragments from the get go as this is the way Android is moving. Only use individual Activities if you really really need to do a quick-and-dirty app for say testing purposes. Fragments, in my opinion, do require a bit more code-work to incorporate and to initially get your head round but it's worth the effort.